For probably more than 20-years now, there has been a maximum flow rate for many water fixtures in a home...on a showerhead, it's 2.5gpm maximum at some pressure (I think at 60psi). If your supply water pressure is lower than that, you may not get as high a volume. But, just like if you try to run splitters, and lots of sprinklers outside off of one hose...when you don't have enough volume available, with all of those outlets, you do not get the acceleration you'd get if the supply isn't larger than the outlets allow...think, putting your finger over the end of a hose...the volume available is the same, but because of the restriction, it sprays further (Bernoulli principle). The design of the showerhead has a huge impact on how the outlet 'feels'. Until you measure the actual flow, you won't know if it's a volume issue or a design issue.